Improvement in pyrometers for steam-engines



G. B. DlXWELL.

Pyrometer for Steam-Eminem Patented March 2,1875.

% gaze/Af UNITED STATES PATENT FFICE.

GEORGE BASIL DIXVELL, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN PVROMETERS FOR STEAM-ENGlNES.

vSpecification forming pa rt of Letters Patent No. 160,40), dated March2, 1875; application liled December 19, 1874.

@Asn B.

To all whom it maglfmucera:

Be it known that l, GEORGE BASIL DIX- WELL, at present a resident otlBoston, ot' the county of Suffolk and State ot' Massachusetts, haveinvented a new and useful Improvement in Steam-Engines, and do herebydeclare the same to be fully described in the ollmving specilication andrepresented in the accompanying drawings, of which- Figure l is a topview, and Fig. 2 a trout elevation, ot' a steam-boiler andengine-cylinder with my invention applied thereto.

Such invention has for its object to obtain, with the smallest possiblechange ol" the existin form ot' steam-engines, the total suppression ofcylinder condensation, and the `greatest amount of further advantagefrom superheating that is compatible with safety to the working parts.rlCliese have'been found, by long and carefullyconducted experiments, tobe uninjured by a temperature a little above 40G@ Fahrenheit in thecylinder, but many engines have been ruined by the use ot' a much highertemperature. I assume, then, that for the present, until betterlubricators are introduced, 4000 Fahrenheit is the limit for the heatot' steam in the cylinder; but 4000 Fahrenheit in the cylinder imports ahigher temperature in the superheater, because, even at full stroke, theentering steam must counterbalance radiation, and at shorter stroke itmust also counterbalance the refrigeration arising out ofthe work doneafter the cut-oil", and this last increases with each increasing measureof expansion. n

Experiments have shown that the heat to counterbalance radiation, andthe conversion ot' heat into power after the eut-off, is taken from themetal of the cylinder, which, in turn, upon the next stroke, absorbs theequivalent from the steam which enters up to the point of cut-oli.

if the steam be suiiiciently superlieated to balance radiation and thework done it will, at the point of ent-oli, be in a state of saturation,without any condensation or forination of mist; but in this case thefull practicable advantage oi' superheating will not be obtained. rthiscan only be donc by adding to the superheated steam in the heater suchfurther temperature as will raise it at the point oi" cut-ott' to 4000Fahrenheit. It is necessary, Y then, to superheat the steam by theamount of the difference between its temperature at saturation and 4000,and also by the equivalent of radiation, and also by the equivalent ot'the work done after the cut-oit". I say the work lone after thecut-ott', because the refrigeration caused by the work done up to thatpoint takes place throughout the whole steam existing` in boilerspipes,and cylinder, and the proportion existing in the cylinder is,especiallyT at short cut-oli", an insigniiicant part of the whole.

Theory would lead us to expect this; and in experiments on a largescale, carefully oonducted and ot' long duration, the amount ot heatabsorbed by the metal from the superheated steam agreed very closely atthe different points ot' cut-oit' with the sum of radiation and theequivalent ot' the work done during expansion.

lt is evident, then, that to maintain the heat in the cylinder at 4G00Fahrenheit requires at each cut-ott a different temperature in thesnperheater, and, in fact, in the experiments above referred to, i000Fahrenheit in the cylinder, at a cut-off ot' seventy per cent., required5300 Fahrenheit in the superheater; 400@ Fahrenheit in Ithe cylinder, ata cut-ott' ot one-hall", required 5680 Fahrenheit; and 4000 Fahrenheitin the cylinder, at one-third cut-oli', required 6260 Fahrenheit in thesuperheater in the engines used. But these diii'erences between thecylinder and superheater temperatures will vary with different engines,because the amount of radiation varies greatly, and we cannot,therefore, rely upon the superheater temperatures to indicate thecylinder temperatures until we have ascertained by experiment thedifferences which actually exist in each particular engine.

Having thus premised, I now proceed to describe the nature or characterof my present invention.

In the accompanying drawings, A denotes the cylinder, and B the boilerand furnace, oi" an ordinary steam-engine, the boiler heilig for theproduction ot superheated steam, to be used eXpansively in the cylinder,which is supposed to be provided with a cut-ott'. The pipe forconveyance of the steam from the geilerator to the steam-chest of thecylinder is shown at U. A pyrometer, D, is arranged in the lower part ofthe cylinder, its stem a being to project through the cylinder, andbeing jointed to an index-pointer, b, to operate with a graduated arc orscale, c, to indicate the temperature of the steam in the cylinder.Another such pyrometer, E, is similarly applied to the steamgenerator orsuperheater, and has its index-pointer d projected over a wooden scaleor platform, e.

I work the engine at a given cut-ott, say, (for instance,) one-third,and note the temperature indicated by the pyrometer in the cylinder,noting, a-lso, at the same time, the temperature in the superheater. ItI tind the temperature in the cylinder to be 4000 Fahrenheit, while thatof the superheater is, say, (5000 Fahrenheit, I make upon the pyrometerscale-board of the superheater, against 6000 Fahrenheit, the wordsone-third cut off.77 I next work the engine at another cut-ott', (say,for instance, one-half,) and if I find that with 4000 Fahrenheit in thecylinder the p vrometer of the superheater shows, say, 5600 Fahrenheit,I mark against 5G00 Fahrenheit of thc pyrometer-sez le of thesuperheater the words one-halt' cut off.7 And so I proceed until thepyrometer of the superheater is, so to speak, graduated for thediiferent cut-offs. I next, it' disposed, withdraw from the cylinder thepyrometer placed in it, and rely thereafter upon the p vrometer of thesul'ierheater, graduated as described.

Fig. 3 denotes the pyrometer-scale, provided with the divisions fortempera-tures, and the marks to indicate the cylinder temperatures fordiiferent cut-offs, as set forth.

In order to audibly indicate the temperature ofthe superheater I applyto the scale of the pyrometer an adjustable metallic slide, f, fixed tothe scale by a elampserew, g, going through a slot in the slide. To thesaid slide j' I attach a wire, h, of an electro-magnetic eurrent, whoseelectro-magnet is shown at c' and battery at 7U'. The armature Z has anelevating-spring, m, and is, `in effect, a hammer to strike a bell, n,arranged over it, as shown. From'the bell a circuit-wire, lL', extendsto and through an electro non-conductor, m', xed upon the index-pointerof the pyrometer of the superheater, and thence is turned toward theslide j".

\Vhen the index-pointer may arrive at the position for which the slideis to be touched by the end of the current-wire carried by the saidindex-pointer, a galvanic circuit will be completed, and the alarm-bellwill be rung. Vhen the engine may have been set to work at a particularcut-oft', the adjustable slide f is to be arranged so that before thecircuit may be completed the index-pointer may have passed a littlebeyond the indicating division of the cut-ott, and whenever this pointis reached the electric bell will give the alarm and the temperature ot`the superheater will be easily diminished by partly closing the damper,or by diminishing` the lire, or by opening the door ot' th efurnace, orany other of the usual means.

There is also applied to the pyrometer-scale another such adjustableslide, j", arranged as shown. Its purpose may be thus explained:

To this auxiliary slide j", and to the non-conductor m of theindex-pointer, circuit-wires o p are attached, and arranged as shown,they leading to the electro-magnetic ala-rm apparatus, or another suchhaving a bell of a tone differing from that of the other bell.

Then it may be desired to have au alarm indicate that the heat in thesuperheater has descended below the equivalent of a previously-selectedminimum, (say, for instance, 3700 Fahrenheit,) the auxiliary slide f isto be adjusted properly to the scale, so that when the degree oftemperature may have been reached the Wire of the index-pointer maybebrought into contact with the auxiliary slide, and thus create closureof the circuit and the sounding of an alarm.

My invention is based upon four facts, which I have discovered lfromexperiments. rIhe first is that superheated steam, unlike the gases,gives up its heat to metallic surfaces, and receives heat from them withgreat rapidity. The second is that the metallic surfaces of the cylinderand piston take up with immense rapidity the excess of heat existing insuperheated steam brought near them, and by their great weight couvert ahigh temperature ot' steam into a much lower temperature of metal. It'we suppose the temperature of the entering steam to exceed thetemperature of the cylinder by, say, 200O Fahrenheit, a very thin filmof the cylinder and piston will sut'iice to reduce this excess from 2000Fahrenheit to 200 Fahrenheit over the original temperature ot' theinternal surfaces. rlhe third is that the said metallic surfaces giveback to the expanding steam the heat previously absorbed, in such amanner as to supply the heat which is converted into work, and the heatwithdrawn b v radiation. The fourth is that diiferent quantities of heatare thus absorbed and given out with diiierent measures of expansion, sothat the steam must, and safely may, be superheated to temperaturesproportioned to the said measures of expansion plus the heat withdrawnby radiation.

I claim as my invention as follows, viz:

1. The combination otl the two pyrometers D E with the superheater B andthe enginecylinder A, to be operated by such, as and for the purposespecified.

2. In combination with the two pyrometers D E, superheater B, and theengine-cylinder A, applied as described, one or more adjustableslides,ff, and one or more electro-magnetic alarms, applied thereto, andto the pyrometer of the superheater, all substantially as and for theobject and purposes as explained and represented.

GEO. BASIL DIXWELL.

Witnesses:

R. H. EDDY, J. It. SNOW.

